Description

Increasingly stringent energy standards and the redesigning of room air conditioners for use with
alternative refrigerants have highlighted the need for design and simulation models that are accurate, easy to modify,
and flexible enough for a variety of design and simulation tasks. This report describes the latest version of the Air
Conditioning and Refrigeration Center (ACRC) room air conditioner simulation model. The model is being continually
improved using heat transfer and pressure drop correlations and other modifications which are added as a result of
an ongoing experimental program.
The governing equations are solved using the Newton-Raphson method, which allows the equations to be
listed in an order-independent fashion. A specialized Newton-Raphson equation solving package was developed
that allows model variables and parameters in the governing equations to be easily "swapped" for design purposes
and includes automated uncertainty and sensitivity analyses.
A two-stage approach toward room air conditioner instrumentation is an integral part of the plans for model
validation and improvement. The first stage uses only air-side thermocouples, and the second stage introduces
refrigerant-side thermocouples and pressure transducers. Comparison of data sets from the two stages allows the
intrusive effects of the refrigerant-side instrumentation to be identified. Simultaneous measurements with air and
refrigerant-side thermocouples make it possible to quantify the offset errors in surface thermocouple measurements
of refrigerant temperatures.
The first stage of the room air conditioner instrumentation has been completed, and a baseline data set has
been taken. The predictions of each component model in the room air conditioner system model are compared with
preliminary experimental results obtained from this non-intrusive instrumentation, and component models which
require improvement are identified. Several appendices address details of the model and equation solver, modeling
condenser condensate spray, and the uncertainty analysis methods and results.

Issue Date:

1994-07

Publisher:

Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.